The present invention relates generally to power conversion systems and more specifically to power conversion in radar antenna systems.
Proper management of power for a destination system, such as conditioning and distribution, often is critical to the operation of the destination system. However, many difficulties complicate the management of power in such systems. For one, many such destination systems include components having different requirements for the form of power supplied. Some components may require an alternating current (AC) electrical feed, others may require direct current (DC) power, and the voltage, current, and/or frequency requirements may differ for different components of the destination system. Another complication often present is that such destination systems often have variable load requirements, making it difficult for conventional power management and distribution systems to provide an adequate amount of power.
Power management is particularly critical in radar antenna systems, where additional difficulties and constraints often are introduced. For example, in addition to different power form requirements, many radar antenna systems, such as Active Aperture Array radar systems, have temporary, rapid increases, or xe2x80x9cpulsesxe2x80x9d, in power consumption during periods of long pulse, high duty scan modes. As a result, the load requirement of the radar antenna varies both substantially and frequently. Likewise, because of the environment in which radar antenna systems typically operate, further consideration is made for the ease of mobility and the ability of the power distribution system to interface with a variety of power sources. Likewise, because of potential hostile actions by adversaries, these radar antenna systems often have certain requirements of the power distribution system with regards to defense, such as by requiring a minimized infrared signature.
Accordingly, various power management systems have been developed to address some or all of these difficulties. However, these known systems have a number of limitations. For one, these known systems typically include a single power source that provides all of the power for the system. Such an arrangement does not accommodate for a failure of the single power source and therefore does not provide redundancy. In response, some known power management/distribution systems include a second power source in parallel with a first power source. Although this arrangement provides redundancy, it too has inherent limitations. Either both power sources must be operational simultaneously, resulting in wasted power/fuel and/or increased operational costs, or only one power source is kept operational at a time, thereby minimizing waste but requiring some down time to switch between one power source to the other power source in the event of a failure or any necessary repairs/maintenance. As a result, degradation in the capability of the power distribution system to provide power generally causes degradation in the performance of the radar antenna system.
Another limitation of known power management systems arises in variable load applications. Conventional power management systems typically provide power at full capacity, thereby causing wasted power during periods of light duty by the destination system. For example, many radar antenna systems operate in a light duty mode a majority of the time and only operate at full capacity during periods of alert, such as when an unknown entity has been detected. Accordingly, to provide for these brief periods of high duty, known radar antenna power systems continuously provide power adequate for the full capacity operation of the radar antenna system, thereby wasting a significant amount of power during light duty periods.
Furthermore, many known power management systems employ power converters to convert power from a first form to power having a second form, such as from alternating current (AC) power to direct current (DC) power. These power converters typically receive power in the first form from one or more power sources, convert the power, and provide the converted power to a component of a system. To illustrate, many types of AC-DC converters include a universal front end where the AC mains typically range between 85 volts AC (VAC) and 265 VAC at between 50 and 60 hertz (Hz). These types of AC-DC converters typically rectify and capacitively filter the AC input to provide a low ripple DC buss to a DC-DC converter.
However, these known converter have a number of limitations. For one, these known converters typically have severe line current harmonics and therefore generally do not comply with Military Standard (MIL-STD) 1399. Also, the high voltage DC buss fed to the DC-DC converter generally is unregulated and fluctuates with line voltage, thereby placing the burden on the DC-DC converter to operate from a 2:1 line range. Furthermore, the output of these known AC-DC converters often are line regulated, requiring a relatively large voltage on the output rectifiers due to the necessary transformer turns ratio. This line regulation requirement often prohibits the optimization of the output state with lowest possible drop Schottky diodes, resulting in a less-than-optimal efficiency and higher power dissipations than otherwise.
Another limitation of many known relatively low voltage power converters is their lack of power factor correction (PFC). This lack of PFC often prevents the power circuitry from achieving optimum performance and meeting critical specifications of the load to which the power converter is connected. Higher voltage (typically above 300 VDC) AC-DC converters can implement PFC relatively easily, since boost or buck-boost style front end can be used to produce a relatively high intermediary voltage. However, the method most typically employed to convert this higher level intermediary voltage to a lower DC output voltage includes placing DC-DC converter in series with the AC-DC converter, thereby increasing the complexity, cost, and power dissipation of the power converter.
Additionally, known power converters typically are not adapted to change their output voltage relative to loading effects, such as a change in the load requirement of a load. Likewise, known power converters generally are incapable of preparing for a heavy load requirement before it occurs. As a result, either a single power converter is adapted to constantly supply an amount of power equivalent to the maximum load requirement of a load or multiple power converters constantly supply a total amount of power equivalent to the maximum load requirement, wasting power in either case. Alternatively, known power converters may be adapted provide only an adequate amount of power for average use. As a result, undesirable operation of the load may occur during heavy loads in excess of the average load requirement. Additional limitations of known power converters include: an inability to produce the desired DC output from a DC input; implementing only a fail signal for the status of the converter, rather than providing built-in test (BIT) or built-in test equipment (BITE) information.
Furthermore, many such power management systems, especially radar systems, make use of voltage regulators to provide a regulated voltage to the one or more loads. However, to account for any temporary increases, or xe2x80x9cpulses,xe2x80x9d in the power consumption by the load, these voltage regulators often include relatively large capacitive elements (e.g., capacitors) both at the input and the output of the voltage regulator to provide stored energy for use during these temporary increases in power consumption. While useful in compensating for the increased power consumption by the load and in preventing the voltage regulator from xe2x80x9cdropping out,xe2x80x9d these relatively large capacitors often prove cumbersome, both in the space they occupy and the cost of their implementation.
The size and cost of these capacitors is of particular significance in radar systems, which often utilize thousands of voltage regulators having both input and output capacitors. As a result, the size of the capacitors has a significant relation to the resulting size of the radar antenna assembly, and as discussed previously, smaller radar systems often provide significant advantages compared to larger radar systems. Likewise, larger capacitors often are more expensive and often generate more heat, while purchasers/operators of radar systems typically seek to minimize both the cost of manufacture and the infrared signature of radar systems.
Accordingly, a system and/or method for improved management of power to variable loads would be beneficial.
The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute part of this specification. The drawings illustrate several exemplary embodiments of the invention and, together with the description, serve to explain the principles of the invention. It will become apparent from the drawings and detailed description that other embodiments, objects, advantages and benefits of the invention also exist.
In a power conversion unit for converting power for use by a variable load, a power conversion unit is provided in accordance with one embodiment of the present invention. The power conversion unit comprises a power conversion circuit having an AC-DC converter having an input and an output and being adapted to convert an AC voltage to an intermediary DC voltage and a DC-DC converter having an input electrically coupled to the output of the AC-DC converter and an output electrically coupled to the variable load, the DC-DC converter being adapted to convert the intermediary DC voltage to an output DC voltage. The power conversion unit further comprises a controller in electrical communication with the power conversion circuit, the controller being adapted to change the output DC voltage from a first voltage to a second voltage based at least in part on information related to the variable load.
In a power management system, an apparatus is provided for converting power having a first form to power having a second form and for providing the power having the second form to at least one variable load in accordance with another embodiment of the present invention. The apparatus comprises a power conversion circuit adapted to convert power having the first form to power having the second form, and means for controlling an output voltage of the power conversion circuit based at least in part on a predicted change in a load requirement of the at least one variable load.
In yet another embodiment in accordance with the present invention, a method for providing power to a variable load using at least one power conversion unit is provided. The method comprising the steps of providing power having a first voltage from the at least one power conversion unit to the variable load at a first time, wherein the first voltage is based on a load requirement of the variable load and determining a second voltage based at least in part on a predicted change in the load requirement of the variable load occurring at a second time subsequent to the first time. The method further comprises the step of temporarily providing power having the second voltage to the variable load at a third time at least prior to the second time and subsequent to the first time.
One advantage of at least one embodiment of the present invention includes minimized power consumption by anticipating a predicted load requirement and providing an adequate amount of power accordingly. Another advantage of the present invention includes minimized power dissipation by activating and deactivating a power converter in accordance with the power requirements of a load. Yet another advantage includes an improved lifespan of the power conversion unit.
Additional features and advantages of the invention will be set forth in the description that follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the systems and methods, particularly pointed out in the written description and claims hereof as well as the appended drawings.